There is known a sheet processing device which performs a post processing such as sorting and stapling on a recording medium (hereinafter, collectively referred to as “sheet”) of a sheet shape conveyed from an image forming device. For example, the sheet processing device includes a standby unit, a processing unit, and a discharge unit. The standby unit temporally retains the sheet. The standby unit sends the retained sheet to the processing unit at a defined timing. The processing unit performs the post processing on the sheet received from the standby unit. The processing unit discharges the sheet subjected to the post processing to the discharge unit.
For example, the processing unit performs sorting and binding on a sheet bundle. The processing unit includes an ejector which supports the rear end of the sheet subjected to the sorting and the binding. The ejector moves from a home position to a downstream side in a sheet conveyance direction while pressing the sheet. The processing unit extrudes the sheet toward the discharge unit by an extrusion member when the ejector is moved up to a predetermined position. In other words, the ejector delivers the sheet to the extrusion member after the sheet is conveyed up to a predetermined delivery position. The ejector returns to the home position when the sheet is delivered to the extrusion member at the delivery position. If a spring is used as a power source for returning the ejector to the home position, there is a possibility to cause an impact noise when the ejector is stopped at the home position. If the impact noise occurs in a housing, the impact noise is propagated and increased, and becomes offensive to a user. Therefore, the ejector is configured to be driven by a motor to decelerate the ejector in front of the home position, so that the impact noise generated at the time of stopping can be suppressed. However, if the motor for driving the ejector is newly provided, the device is likely to be increased in size.